Immune System

immediate, general defense against pathogens present from birth.

innate (nonspecific) immunity

Slower, targeted immune response that develops after exposure and forms memory.

adaptive (specific) immunity

Innate =

fast, no memory, nonspecific

Adaptive =

slow, memory, highly specific

Where do T cells mature?

the thymus

What is the main function of helper T cells (CD4⁺)?

Activate B cells and cytotoxic T cells using cytokines.

What is the main function of cytotoxic T cells (CD8⁺)?

Directly kill infected or cancerous cells.

What do regulatory T cells do?

Suppress immune responses to maintain tolerance

Where do B cells mature?

bone marrow

What is the main function of B cells?

produce antibodies

What do activated B cells differentiate into?

plasma cells and memory B cells.

Large phagocytic cells that engulf pathogens and present antigens.

macrophages

Where are macrophages found?

tissues throughout the body

Cells that ingest and destroy pathogens.

ex. Neutrophils, macrophages, dendritic cells.

phagocytes

What process do phagocytes use to destroy pathogens?

phagocytosis

What is the role of bone marrow in immunity?

Production of blood cells; B-cell maturation.

Filters blood, removes pathogens, stores immune cells.

spleen

What is the function of the thymus?

Maturation of T lymphocytes.

What happens to the thymus with age?

It shrinks (involution)

What is the function of lymph nodes?

Filter lymph and activate immune responses.

Why do lymph nodes swell during infection?

Rapid lymphocyte proliferation.

Any substance that triggers an immune response

antigen

A protein made by B cells that specifically binds an antigen.

antibody

What is the main function of antibodies?

Neutralize pathogens and tag them for destruction.

Display of antigen fragments on MHC molecules for T-cell recognition.

antigen presentation

Which cells present antigens?

Macrophages, dendritic cells, B cells

Which MHC presents to helper T cells?

MHC II

Which MHC presents to cytotoxic T cells?

MHC I

Process where antigen activates only specific lymphocytes.

clonal selection

What happens after clonal selection?

Proliferation and differentiation into effector and memory cells.

What determines antigen–antibody binding specificity?

Shape and chemical complementarity.

the specific antigen region that an antibody binds.

epitope

What is the basic structure of an antibody?

two heavy and two light chains

What bonds hold antibody chains together?

disulfide bonds

which region binds antigen?

Variable (Fab) region.

Which region determines immune response type?

Constant (Fc) region.

Ability to avoid attacking self tissues.

immune tolerance

A condition where the immune system attacks self tissues.

ex. type 1 diabetes, lupus, rheumatoid arthritis

autoimmune disease

Set of cell-surface proteins that display antigen fragments.

MHC

What is the role of MHC I?

Displays intracellular antigens to cytotoxic T cells.

What is the role of MHC II?

Displays extracellular antigens to helper T cells.

Why is MHC important in organ transplantation?

Mismatched MHC leads to graft rejection.

B cells =

antibodies

T cells =

regulation + killing

Macrophages + dendritic =

antigen presentation

Bone marrow =

B cells

Thymus =

t cells

Spleen =

blood filter

Lymph nodes =

lymph filter

Antigen =

trigger

Antibody =

binding protein

Clonal selection =

specific activation

MHC I →

CD8

MHC II →

CD4

Autoimmunity =

self-attack